I am hitting my OG's, but the FG seems to be off by about 5 points or so. This just doesn't make sense to me. I am using a starter with Wyeast or WL. Not sure how I can make an improvement on this. Thoughts?

Airation may be a factor. If the yeast are running out of gas and not multiplying enough to get the job done, then oxygen may be a factor. If you are using extract, it may be the fermentability of the extract.

How confident are you in your thermometer? If your thermometer is reading a little low, then you could accidentally be mashing, say, at 158, which would reduce your fermentability a bit. Try mashing lower, see how the beers turn out.

Also, try a fancy-pants aeration system if you feel like spending a few bucks.